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Tracing the stepwise oxygenation of the Proterozoic ocean.
Nature. 2008 Mar 27; 452(7186):456-9.Nat

Abstract

Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth's atmosphere. Geochemical data suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichments indicative of persistent and vigorous oxidative weathering appear in shales deposited at roughly 2,150 Myr ago, more than 200 million years after the initial rise in atmospheric oxygen. Subsequent expansion of sulphidic conditions after about 1,800 Myr ago (refs 8, 9) maintained a mid-Proterozoic molybdenum reservoir below 20 per cent of the modern inventory, which in turn may have acted as a nutrient feedback limiting the spatiotemporal distribution of euxinic (sulphidic) bottom waters and perhaps the evolutionary and ecological expansion of eukaryotic organisms. By 551 Myr ago, molybdenum contents reflect a greatly expanded oceanic reservoir due to oxygenation of the deep ocean and corresponding decrease in sulphidic conditions in the sediments and water column.

Authors+Show Affiliations

Department of Earth Sciences, University of California, Riverside, California 92521, USA. cscot002@ucr.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Historical Article
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

18368114

Citation

Scott, C, et al. "Tracing the Stepwise Oxygenation of the Proterozoic Ocean." Nature, vol. 452, no. 7186, 2008, pp. 456-9.
Scott C, Lyons TW, Bekker A, et al. Tracing the stepwise oxygenation of the Proterozoic ocean. Nature. 2008;452(7186):456-9.
Scott, C., Lyons, T. W., Bekker, A., Shen, Y., Poulton, S. W., Chu, X., & Anbar, A. D. (2008). Tracing the stepwise oxygenation of the Proterozoic ocean. Nature, 452(7186), 456-9. https://doi.org/10.1038/nature06811
Scott C, et al. Tracing the Stepwise Oxygenation of the Proterozoic Ocean. Nature. 2008 Mar 27;452(7186):456-9. PubMed PMID: 18368114.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Tracing the stepwise oxygenation of the Proterozoic ocean. AU - Scott,C, AU - Lyons,T W, AU - Bekker,A, AU - Shen,Y, AU - Poulton,S W, AU - Chu,X, AU - Anbar,A D, PY - 2007/06/15/received PY - 2008/01/31/accepted PY - 2008/3/28/pubmed PY - 2008/5/1/medline PY - 2008/3/28/entrez SP - 456 EP - 9 JF - Nature JO - Nature VL - 452 IS - 7186 N2 - Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth's atmosphere. Geochemical data suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichments indicative of persistent and vigorous oxidative weathering appear in shales deposited at roughly 2,150 Myr ago, more than 200 million years after the initial rise in atmospheric oxygen. Subsequent expansion of sulphidic conditions after about 1,800 Myr ago (refs 8, 9) maintained a mid-Proterozoic molybdenum reservoir below 20 per cent of the modern inventory, which in turn may have acted as a nutrient feedback limiting the spatiotemporal distribution of euxinic (sulphidic) bottom waters and perhaps the evolutionary and ecological expansion of eukaryotic organisms. By 551 Myr ago, molybdenum contents reflect a greatly expanded oceanic reservoir due to oxygenation of the deep ocean and corresponding decrease in sulphidic conditions in the sediments and water column. SN - 1476-4687 UR - https://www.unboundmedicine.com/medline/citation/18368114/Tracing_the_stepwise_oxygenation_of_the_Proterozoic_ocean_ L2 - https://doi.org/10.1038/nature06811 DB - PRIME DP - Unbound Medicine ER -